Absorption refrigeration machine

ABSTRACT

An absorption refrigeration system employing a generator having a heat pipe associated therewith to transfer heat from a suitable burner to the interior of the generator to increase the capacity of the generator without a proportionate increase in the size thereof and to minimize the inside surface temperature of the generator wall.

Elite States atent Gable [451 Sept. 26, 1972 [54] ABSORPTIONREFRIGERATION 464,434 12/ 1891 Hill ..122/33 X MACHINE FOREIGN PATENTSOR APPLICATIONS [72] Inventor: Gerald K. Gable, 7654 Villa Maria,

North Syracuse, N Y 13212 454,585 Canada ..122/33 [22] Flled' 1971Primary Examiner-William F. ODea [21] Appl. No.: 117,274 AssistantExaminerP. D. Ferguson I Attorney-Harry G. Martin, Jr. and .1. RaymondCur- [52] US. Cl. ..62/476, 62/497, 122/33,

165/105 51 Int. Cl. ..F25b 15/04, F22b 1/02 1571 ABSTRACT of Search Anabsorption refrigeration system employing 3 165/105 generator having aheat pipe associated therewith to transfer heat from a suitable burnerto the interior of [56] References cue! the generator to increase thecapacity of the generator UNITED STATES PATENTS without a proportionateincrease in the size thereof and to minimize the inside surfacetemperature of the 44,153 9/1864 Bayley ..122/33 generator n 3,254,5076/1966 Whitlow ..62/497 X 3,520,282 7/1970 Fisher ..62/497 X 3 Claims, 1Drawing Figure ABSORPTION REFRIGERATION MACHINE BACKGROUND OF THEINVENTION In fuel-fired absorption refrigeration machines it isdifficult to transfer heat from the flue gas to the solution within thegenerator without heating the generator wall to a temperature whichpermits corrosion of the generator and deterioration of the solutiontherein. For desired machine efficiency, the greatest quantity of heatpossible should be transferred from the flue gas to the solution.

One of the common means for accomplishing this purpose is to providefins on the generator to transfer the heat to the generator wall andsubsequently to the solution therein. However, the combustiontemperature adjacent the burner is often high enough to oxidize the finsor to produce an excessive generator wall temperature which couldaccelerate corrosion of the generator and cause premature failurethereof.

SUMMARY OF THE INVENTION The present invention relates to an absorptionrefrigeration system comprising a generator, an absorber, a condenserand an evaporator, first tubular heat transfer means disposed adjacentthe exterior of the generator, combustion means disposed adjacent thegenerator and the first heat transfer means for directly heating thegenerator and the first heat transfer means, and second tubular heattransfer means disposed interiorly of the generator communicating withthe first tubular heat transfer means, the first and second heattransfer means being adapted to transfer heat produced by the combustionmeans to'the solution within the generator to heat the solution andincrease the amount of heat transferred from the combustion means to thesolution without increasing the amount of heat transferred through thegenerator wall or increasing the inside surface temperature of the wall.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic diagram ofan absorption refrigerationsystem employing the improved generator ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, thereis shown an absorption refrigeration system comprising an absorber 10, acondenser 12, and evaporator or chiller 14, a generator 16, aliquid-suction heat exchanger 18, and a vapor distributor 20 connectedto provide refrigeration. A pump 22 is employed to circulate weakabsorbent solution from absorber to generator 16.

As used herein, the term weak absorbent solution refers to solutionwhichis weak in absorbent power, and the term strong absorbent solution"refers to a solution which is strong in absorbent power. A suitableabsorbent for use in the system described is water; a suitablerefrigerant is ammonia.

Liquid refrigerant condensed in condenser 12 passes through refrigerantliquid passage 24vto the liquid-suction heat exchanger. Theliquid-suction heat exchanger 18 includes a housing 26 having arefrigerant restrictor 28 at the upstream end and a refrigerantrestrictor 30 at the downstream end thereof. A portion of the liquidrefrigerant supplied to the liquid-suction heat exchanger 18 flashesupon passing through restrictor 28 due to the low pressure existingdownstream of the restrictor, thereby cooling the remainder of therefrigerant in the housing 26. The cooled refrigerant liquid and flashedrefrigerant vapor then pass through restrictor 30 into heat exchanger 32of chiller 14.

A heat exchange medium such as water is passed over the exterior of heatexchanger 32 where it is chilled by giving up heat to evaporate therefrigerant within the heat exchanger. The chilled heat exchange mediumpasses out of chiller 14 through line 34 to suitable remote heatexchangers (not shown) after which it is returned to the chiller throughinlet 36 for rechilling.

The cold refrigerant evaporated in heat exchanger 32, along with a smallquantity of absorbent which is carried over to the chiller with therefrigerant from the generator, passes into refrigerant vapor passage 38of liquid-suction heat exchanger 18. The refrigerant vapor and absorbentliquid, which has a large quantity of refrigerant absorbed therein,passes through refrigerant vapor passage 38 in heat exchange relationwith the refiigerant passing through housing 26. Refrigerant vapor andabsorbent solution from passage 38 passes to refrigerant distributor 2.0through line 42. The

refrigerant vapor and absorbent solution from line 42 are mixed withsolution from the generator 16 which is supplied to to the distributorthrough line.

The absorbent solution-refrigerant vaporv mixture from distributor 20 issupplied to absorber 10 where a cooling medium, preferably ambient air,is passed over the surface of the absorber in heat exchange relationwith the solution therein for cooling the absorbent solution to promotethe absorption of the refrigerant vapor by the solution. The samecooling medium may be supplied to condenser 12 in heat exchange relationwith refrigerant vapor therein to condense the refrigerant.

Cold weak absorbent solution passes from absorber 10 through line 46into the pump 22. Liquid from pump 22 is passed through line 48 torectifier heat exchange coil 50. The weak solution passes through coil50 in heat exchange relation with hot strong solution passing throughheat exchange coil 52 disposed within coil 50 and with the hotrefrigerant vapor flowing through rectifier shell 54 in contact with theouter surface of coil 50. The weak solution from coil 50 is dischargedinto the upper portion of generator 16 along with any vapor which isformed in coil 50 due to heat exchange with the hot vapor passingthereover and the hot solution flowing therethrough.

Generator 16 comprises a shell 56 having fins 58 suitably affixedthereto as by welding. The generator is heated by a gas burner v60 orother suitable heating means. A heat exchanger or heat pipe 62comprising a coil 64 external of the generator and a coil 66 on theinterior of the generator is provided to transfer heat from the burner60 to the solution within generator 16. The heat pipe 62 is formed of asuitable material such as stainless steel which is resistant tocorrosion at the high temperature produced by the burner 60. The heatpipe is partially filled with a suitable heat exchange medium such asdistilled water. The heat from burner 60 vaporizes the heat exchangemedium in coil 64. The vapor from coil 64 passes through fitting 70 intocoil 66 within the generator where it is condensedby giving up heat tothe solution in the generator. Thecondensed heat exchange medium fromcoil 66 passes through drain line 68 to coil 64 where it is againvaporized for subsequent passage through line 70 to coil 66.

By locating the outer coil of the heat pipe in close proximity to thelower surface of the generator vessel, the heat from the burner istransferred both to the generator and to the outer coil of the heatpipe. The total surface area exposed to the flue gas, which includesboth the exterior surface of the generator and the exterior surface ofthe outer heat pipe coil, provides a large heat exchange surface fortransferring heat from the flue gas. The increased quantity of heattransferred from the flue gas to the total heat exchange surface resultsin decreased flue temperatures. At the same time, the increased surfacearea exposed to the flue gas and the efficient transfer of heattherefrom to the solution within the generator through the interior coilof the heat pipe, results in increased heat input to the generatorwithout an increase in generator inside wall temperature. I

The heat transfer surface within the generator is also increased by theuse of a heat pipe since thetotal surface exposed to the solution withinthe generator includes both the interior wall surface of the generatorand the surface of the inner coil of the heat pipe. A greater quantityofliquid is exposed to the increased interior heat transfer surface,thereby allowing a greater quantity of heat tobe transferred thereto.

For a given heat input, as the heat transfer surface is increased, thesurface wall temperature decreases. The exterior coil of the heat pipein conjunction with the exterior wall of the generator providesincreased heat transfersurface to extract more heat from the flue gaswhile at the same time, the increased heat transfer surface area exposedto the solution within the generator allows the increased quantity ofheat obtained from the flue gas to be transferred to the solution at alower temperature than has heretofore been possible with direct firedabsorption machines.

The temperature of the solution within the generator is ordinarily afunction of the boiling point of the solution at the pressures existingwithin the machine. However, since a large quantity of heat must betransferred to the solution, the solution nearest the heat transfersurface may be heated to a temperature substantially above the boilingpoint. By increasing the heat exchange surface area within thegenerator, a greater quantity of heat may be transferred to the solutionwhile maintaining the solution adjacent the heat exchange surface at atemperature nearer the boiling point of the solution. Therefore, byutilizing the heat pipe, the generator wall temperature and thetemperature of the solution within the generator is reduced, while atthe same time the flue gas temperature discharged from the generator isalso reduced. Thus, a greater quantity of heat is supplied to thesolution than has been possible heretofore even though the temperatureof the solution and the generator wall is materially reduced.

The weak solution which is boiled in generator 16 concentrates thesolution, thereby forming strong solutio an refri erant va or.

The hot stong abs rbent solution passes upwardly through the analyzersection of generator 16, through analyzer coil 76 in heat exchange withthe weak solution passing downwardly over the coil. The warm strongsolution then passes through heat exchange coil 52 within coil 50 andline 44 into the distributor 20. A restrictor 78 is provided in line 44so that the solution supplied to the vapor distributor 20 is at the samepressure as the vapor in line 42.

Refrigerant vapor formed in generator 16 passes upwardly through theanalyzer section thereof where it is concentrated by mass heat transferwith weak solution passing downwardly over analyzer coil 76. Analyzerplates 80 in generator 16 provide a tortuous path for flow of solutionand vapor to assure intimate contact therebetween to improve the massheat transfer. The

vapor then passes through rectifier 54 in heat exchange relation withthe weak solution passing through coil 50. Absorbent condensed inrectifier 54 flows downwardly into the generator along with the weaksolution discharged from coil 50. Refrigerant vapor passes fromrectifier 54 through line 82 to condenser 12 to complete therefrigeration cycle.

While I have described a preferred embodiment of my invention, it is tobe understood that the invention is not limited thereto since it maybeotherwise embodied within the scope of the following claims.

I claim:

1. An absorption refrigeration system including a cylindrical generator,an absorber, a condenser, and an evaporator, said generator beingadapted to receive solution to be vaporized;

first tubular heat transfer means comprising a tubular coil encirclingthe exterior of said generator and spaced therefrom to form an annulusbetween said coil and said generator;

combustion means disposed adjacent said first tubular heat transfermeans and said generator for heating the walls of said generator andsaid first tu bular heat transfer means, passage of flue gas throughsaid annulus heating the walls of said generator and said tubular coil;

second tubular heat transfer means disposed interiorly of said generatorcommunicating with said first tubular heat transfer means fortransferring heat from said first tubular heat transfer means to saidsecond tubular heat transfer means to increase the amount of heattransferred to the solution inside said generator and minimize thequanti ty of heat transferred from said combustion means through thewalls of said generator to solution therein, thereby minimizing theinside surface temperature of the walls of said generator.

2. An absorption refrigeration system according to claim 1 wherein saidsecond tubular heat transfer means comprises a tubular coil disposed inthe lower portion of said cylindrical generator.

3. An absorption refrigeration system according to claim 2 wherein saidfirst and second tubular heat transfer means contain a heat exchangefluid for circulation therein, said heat exchange fluid when cooloccupying only a portion of the space within saidcoils.

1. An absorption refrigeration system including a cylindrical generator,an absorber, a condenser, and an evaporator, said generator beingadapted to receive solution to be vaporized; first tubular heat transfermeans comprising a tubular coil encircling the exterior of saidgenerator and spaced therefrom to form an annulus between said coil andsaid generator; combustion means disposed adjacent said first tubularheat transfer means and said generator for heating the walls of saidgenerator and said first tubular heat transfer means, passage of fluegas through said annulus heating the walls of said generator and saidtubular coil; second tubular heat transfer means disposed interiorly ofsaid generator communicating with said first tubular heat transfer meansfor transferring heat from said first tubular heat transfer means tosaid second tubular heat transfer means to increase the amount of heattransferred to the solution inside said generator and minimize thequantity of heat transferred from said combustion means through thewalls of said generator to solution therein, thereby minimizing theinside surface temperature of the walls of said generator.
 2. Anabsorption refrigeration system according to claim 1 wherein said secondtubular heat transfer means comprises a tubular coil disposed in thelower portion of said cylindrical generator.
 3. An absorptionrefrigeration system according to claim 2 wherein said first and secondtubular heat transfer means contain a heat exchange fluid forcirculation therein, said heat exchange fluid when cool occupying only aportion of the space within said coils.